Garmin G1000 Manual page 357

Integrated flight deck

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The role of radar is essentially to detect moisture in the atmosphere. Simply put, certain types of weather

reflect radar better than others. The intensity of a radar reflection is not necessarily an indication of the

weather hazard level. For instance, wet hail returns a strong radar reflection, while dry hail does not. Both

wet and dry hail can be extremely hazardous.

The different NEXRAD echo intensities are measured in decibels (dB) relative to reflectivity (Z). NEXRAD

measures the radar reflectivity ratio, or the energy reflected back to the radar receiver (designated by the

letter Z). The value of Z increases as the returned signal strength increases.

NEXRAD radar images may have certain limitations:

• NEXRAD base reflectivity does not provide sufficient information to determine cloud layers or precipitation

characteristics. For example, it is not possible to distinguish between wet snow, wet hail, and rain.

• NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. An individual NEXRAD

site cannot depict high altitude storms at close ranges. It has no information about storms directly over

• When zoomed in to a range of 30 nm, each square block on the display represents an area of four square

kilometers. The intensity level reflected by each square represents the highest level of NEXRAD data

sampled within the area.

• Any unknown precipitation type below 52ºN is displayed as rain.

190-00709-05 Rev. D

Garmin G1000 Pilot's Guide for the Socata TBM 850/900

Figure 6-12 NEXRAD Data - Zoomed

HAZARD AVOIDANCE

covers an Area

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